RADIATIVE DECAYS OF EQUAL MASS VECTOR MESONS IN A BETHE–SALPETER EQUATION FRAMEWORK

In this work, we have employed Bethe–Salpeter equation (BSE) under Covariant Instantaneous Ansatz (CIA) to study radiative decays of light vector mesons through the process: h→h'γ, taking h and h' as equal mass light vector and pseudoscalar mesons, respectively. The decay widths calculated for these processes are in reasonable agreement with data. The motivation for this work was our intention to resolve the problems involved in calculations of triangle quark-loop diagrams which appear in processes such as radiative meson decays, meson form factors, strong decays of mesons, etc., in BSE under CIA, which give rise to complexities in amplitudes (as pointed out earlier in Ref. 1) due to the presence of the time-like momentum components in Gaussian factors associated with the vertex functions of the participating hadrons. In this work we try to highlight this problem and then demonstrate a mathematical procedure which might lead to calculations of such processes in BSE under CIA.

MESON PVV INTERACTIONS ARE DETERMINED BY QUARK LOOPS

We show that all abnormal parity three-body meson interactions can be adequately described by quark loops, evaluated at zero external momentum, with couplings determined by U(Nf) symmetry. We focus primarily on radiative meson decays which involve one pseudoscalar. The agreement with experiment for nonrare decays is surprisingly good and requires very few parameters, namely the coupling constants gπqq and gρqq and some mixing angles. This agreement extends to some three-body decays that are dominated by pion pairs in a P-wave state.

Quark Triangle Diagrams and Radiative Meson Decays

The radiative meson decays V→ Pγ and P →γγ are analysed using the quark triangle diagram. Experimental data yield well determined estimates of the universal quark–antiquark–meson couplings gvqq′ and gpqq′ for the light meson sector. Also predictions for the ratios of neutral to charged heavy meson decay coupling constants are given and await experimental confirmation.